Herenton has been all over the map in recent months, first saying he would resign his mayoralty to run against Cohen, then delaying his resignation. He finally resigned, but then pulled a shocker by pulling a petition to run in the special election to reclaim his old post.

Herenton went on local radio last week to insist, over the host's suggestions, that he hadn't gone "crazy."

Now, Herenton says he will not run in the special election and will indeed challenge Cohen. And the all-too-blunt longtime mayor is continuing his vulgar and racially tinged assault on Cohen, labeling him "an a**hole."

Cohen represents a majority black district, which has made him susceptible to primary challenges.

"I can't think of a better description of Steve Cohen," he said. "He was an a**hole three weeks ago. And he's an a**hole now. To know Steve Cohen is to know he doesn't think very much about African-American people. He has a notion of superiority and he has temper tantrums."